This invention relates to closures in general and tube or pipe end closures for threaded plastic pipes in particular.
Plastic piping is used in many industrial settings. It is lightweight, easy to fabricate, relatively inexpensive, and non-reactive to many materials. Plastics have particular relevance in the semiconductor fabrication industry where ultra-pure conditions are often required. Piping systems are usually laid out in anticipation of future additions or modifications. This makes it relatively easy to tie into or remove portions of the system as required. For example, a space reserved for a future addition such as a processing apparatus may be terminated close to where the anticipated connection is to be located. Normally, when temporarily tying off or closing a pipe or tube, particularly a pipe or tube with threaded ends, the pipe end is provided with a threaded cap or a valve. These devices of temporarily closing off a pipe end have their drawbacks. With threaded caps, sealing is accomplished by the threads or a gasket material, or a combination of threads and a gasket material. This approach does not work particularly well in semiconductor fabrication situations which require corrosive and/or high temperature fluids. Corrosive fluids used in semiconductor processing often reacts with piping and gaskets causing degradation and leaching, which in turn contaminates the fluid. High temperatures speed up the process of degradation. Further, for high pressure situations, a cap will be torqued tighter onto the pipe increasing the possibility of damage to threads of both the pipe and the cap and/or mechanical abrasion which creates contamination. Valves are acceptable, but expensive. Even with valves, when the tube or pipe end is subsequently connected to other devices, additional connectors and their attendant tools are often required to enable attachment to the original pipe or tube. This requires additional fixtures and man hours to connect the various components.
Closures are known which utilize a nut to secure a flared cap on a ripple. With removal of the nut, the flared cap stays on the nipple until a sufficient axial cap removal force is applied. Such caps are often difficult to grasp by hand and gripping tools can damage the plastic parts.
The present invention solves the problems inherent to the above-mentioned methods of capping or tying off a tube or pipe end by providing a tube closure which works in concert with existing pipe fittings and facilitates removal of the cap.
Another object of the invention is to create smooth interior transitions between a pipe or tube and a closure.
It is an object of the present invention to provide a twopiece closure mechanism for a pipe or tube end which may be easy manufactured by injection molding.
Another object of the invention is to provide a snug fitting cap for a pipe or tube end.
Another object of the invention is to facilitate removal of a snug fitting cap from a pipe or tube end.
Yet another object is to permit temporary retention of a cap onto a pipe or tube end by a retainer or nut.
Another object of the present invention is to enable a pipe or tube end to be closed or tied off without the assistance of tools.
Still another object of the present invention to eliminate the use of gasket material in a pipe or tube closure.
Another object of the invention is to increase the amount of sealing area between a pipe or tube and a closure mechanism.
Still another object of the invention is to provide a contaminant-free closure for a pipe or tube end.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.